The Nervous System Part 2- Electrical Activity in Axons and the Synapse Flashcards
Na+ is more concentrated ________ and K+ is more concentrated ________.
Na+ - Extracellularly
K+- Intracellularly
Play into the potential difference and charges of the cell.
Excitability/Irritability refers to what?
A physiology aspect of neurons and muscle cells abilities to produce and conduct changes in membrane potential.
When the membrane permeability increases for a specific ion, which results in movement of that ion down its concentration gradient, what kind of an environment is that happening in?
A very small localized environment. It doesn’t mean the whole cell becomes permeable to the ion, just a limited specific patches of the membrane where specific ion channels are located.
What does an oscilloscope show?
Shows the voltage between two recording electrodes over time displayed as a line. Measuring the changes in potential difference inside and outside a membrane.
Resting Membrane Potential in Neurons?
-70 mV
Resting membrane potential in heart muscle cells?
-85 mV
Depolarization (Excitatory)
caused by the opening of Na+ channels, called depolarization because if using a oscilloscope the potential difference between the extracellular electrode and intracellular electrode would become less different (inside is becoming more positive)
A return to resting membrane potential is known as?
Repolarization
What is the period called when the inside of the cell becomes more negative than the resting membrane potential?
Hyperpolarization (Inhibitory)
What are the two types of channels for K+
Voltage Gated Channel- The gate is closed at resting membrane potential.
A Channel that is NOT gated- Called “leakage” channel, always open.
What are the channels like for Na+?
They are all gated, and the gates are closed at the resting membrane potential. (sometimes they flicker allowing small amounts of Na+ into the cell)
What is the threshold in neurons? and at what point does it have to be reached if an action potential is to be generated?
Threshold: -55 mV
Needs to reach threshold by the initial segment of the axon.
What happens when threshold is met?
Na+ Channels open, Na+ rushes into the cell. (remember this is happening at a very specific and small region of the cell)
=DEPOLARIZATION
Na+ channels are only open for a fraction of a second, quick ball and chain (a polypeptide chain) closes them quickly.
What is +30 mV (sometimes said to be +40 mV)
It is the Peak of the Action Potential.
Depolarization is caused by opened Na+ channels. Those channels however close due to an inactivation process, but just before they do the depolarization stimulus causes what?
Causes the gated K+ channels to open. Causes the membrane potential to move toward potassium equilibrium potential (K+ is rushing out of the cell at the localized spot).
=REPOLARIZATION
Na+ and K+ channels are both stimulated by depolarization, that makes those ion channels in the axon membrane ____ ____ channels.
Voltage Gated Channels
Na+ channels depolarizing leads to the opening of even more Na+ voltage gated channels opening. What feedback is utilized?
Positive Feedback Loop.
K+ channels open due to the depolarization of the cell, causing K+ to rush out of the cell, driving the membrane potential back towards the resting membrane potential, repolarization, what feedback is completed here?
Negative Feedback Loop.
The changes of Na+/K+ diffusion and the resulting changes in the membrane potential they produce, constitute an event called what?
Action Potential / Nerve Impulse
Opening of Voltage Gated K+ channels causes repolarization of the cell. But the K+ causes the membrane potential to slightly overshoot the resting membrane potential, what is this period called?
Hyperpolarization, or after-hyperpolarization. Just dips below resting potential of -70 mV, doesn’t actually reach the membrane permeability for K+ which would be -90 mV.
What pump is required to maintain the concentration gradients needed for the diffusion of Na+ and K+ during action potentials? These same pumps are also required to move Na+ out of the axon and to move K+ back into the axon after an action potential to restore resting conditions.
Na+/K+ pump
-If a neuron was poisoned with cyanide it could still produce action potentials for a limited time, because it uses diffusion methods to create an action potential. But without ATP to utilize the Na+/K+ pumps, eventually there wouldn’t be a gradient that allowed for nerve impulses.
An increase in frequency is what shows a larger stimuli in action potentials, not an increase in amplitude. Action potentials are therefore said to be an “____ _ ____ ___”
All or Nothing Event.
